2. Place filters in the walk-in freezer
until ready to analyze. Also, use the Manual for the Perkin-Elmer CHN
analyzer to assist you; most of the
steps outlined below are also
discussed in the Manual (Currently
we are using a PE 2400 Series II
CHNS/O Analyzer).

3. On the day before the filters are to be
pelletized, place them in a drying
oven at 37C for at least 12 hours. Then transfer the dried filters to
a desiccator. Pull a vacuum on the desiccator if
possible.
If the filters are dried at Toolik
at 55 C this isn’t as important
especially if Hydrogen values are
not important.

4. Take the filters to the instrument room
(3rd
floor, Loeb or 3rd floor
Starr ).
Tear off a section of aluminum foil
to use as a work surface.
Get the tin disks and forceps from the drawers beneath the CHN analyzer
and the balance.
Clean the forceps thoroughly with
kimwipes.
Use the forceps to handle the tin
disks and the filters; do not use
your fingers!

5. To pelletize a filter, center the filter
on a tin disk, sample side up.
Make sure you have only one tin
disk; they're very thin and it's
easy to pick up more than one at
once.
With the forceps, fold the disk in
half so that the filter is on the
inside. Fold the disk again lengthwise
(you should now have a long thin
strip rather than a quarter-circle;
see the manual).

6. Fold the ends of the strip over, and
then roll the burrito up.
If you roll it up too tightly, you
may rip the tin, so be careful. When it is rolled up, no part of the filter inside
should be visible.

7. Place the "burrito" into the pelletizing
cylinder.
Put the cylinder in the wide
mouth-side of the stage mount.
Pull down the handle part way and
line up the press with the opening
of the cylinder.
When they are lined up, pull the
handle all the way down and press
the burrito.

8. Lift the handle and remove the cylinder.
Flip the stage mount over so that
the narrow-mouth side is up.
Put the cylinder back on the stage,
line up the press and the opening,
and pull the handle down.
The press will knock the pellet into
the narrow-mouth opening.

9. Using the forceps, remove the pellet and
place it into a pellet-holding tray
(there are several trays in the
instrument room).
It is essential that you keep track
of which pellet is in which hole in
the tray. The holes in the trays are marked (A1, A2, A3, etc. ), so use the data sheets provided
(titled "AUTO RUN Sample Information
(Filters)" or make your own) to
record which pelletized sample is in
which hole.
Leave the first row (A1-A12) empty; you will put your initial standards
and blanks in that row.
About every 10 pellets, skip two
holes (a standard blank and a filter
blank will go in these holes).

10. Calibrate the balance in the corner,
using the instructions provided in
the booklet on top of the balance. The
calibration weights are in the
drawer under the balance. The range setting should be 20 mg.

11. Pack standard blanks (also called a K factors): The K factor Is a standard of known
amount of acetanilide

1. Place an ashed 25-mm GF/F filter on a
tin disk, fold them in half with the
forceps, and then unfold partially
so that there is a crease down the
middle of the filter and tin.

2. Place a counterweight pellet on the left
pan of the balance (there are
several counterweights in a small
plastic box; however, some were made
with more than one tin disk and will
cause an error on the scale, so keep
trying until you get the
counterweight with only one tin
disk).

3. Place the creased filter and disk on the
right pan of the balance, lower the
pan arrest, and zero the balance.
Raise the pan arrest.

4. Using the spatula, place a small amount
of acetanilide on the creased
filter.
Lower the pan arrest and check the weight. Add or remove acetanilide until you have between 2 and
3 mg of acetanilide.
Record the weight on a Preliminary
Standardization Data Sheet
(available in folder on table in the
CHN room).

5. VERY CAREFULLY, using the two pairs of
forceps, roll up the disk into a
sausage as described above. Make
sure you don't spill any of the
acetanilide and that you don't rip
the tin. Start over if you do either of these
things, or else the weight in the
next step will not be correct.

6. Pelletize the sausage and reweigh. If the weight is greater or less
than the original weight by more
than about 0.
010 mg, start over. If
not, then record the second weight.

7. Still using the forceps, place the
pellet in a designated hole in the
pellet tray.
The first five K factor pellets will go on row A (in holes A1, A3, A5,
A7, and A9).
Subsequent K factor pellets will go
within the samples; as you recall,
every ten samples or so, you left
two holes blank.
The first of these holes is for a K
factor.
So, place the K factor pellet in the
first of a pair of empty holes and
record the hole number and the
weight of the acetanilide in the K
factor pellet on the data sheet (use
the Preliminary Data Sheet if the
pellets are going into row A and the
Auto Run Sample Inf. data sheet if
the pellets are being implanted
within the samples).

12. Pack filter blanks:

1. Using the forceps, place a blank 25-mm
GF/F filter that you brought back
from the field onto one of the tin
disks.

2. Pelletize the blank filter in the same
manner as the sample filters
(described above); do not add
acetanilide.

3. Transfer the pelletized blank filter to
the pellet tray.
Place in one of the empty holes
designated for blanks. The first
four blanks will go on row A (in
holes A2, A4, A6, and A8).
Subsequent blanks will go within the
samples; as you recall, every ten
samples or so, you left two holes
blank.
The second of these holes
is for a blank.
So, place the blank pellet in the
second of a pair of empty holes and
record the hole number on the data
sheet (use the Preliminary Data
Sheet if the pellets are going into
row A and the Auto Run Sample Inf.
data sheet if the pellets are being
implanted within the samples).

13. At this point, you are ready to run your
samples.
If, however, the CHN machine is
already in use or not ready to run,
tape your pellet trays shut, label
them, and place them in a desiccator
with activated desiccant and draw a
vacuum on them until the machine is
available.

14. When the machine is available, check
with Don Burnette to make sure that
there is enough helium, oxygen, and
nitrogen gas, and that the columns
are fresh enough to run all of your
samples.

15. The PE 2400 must be programmed to
run filters and therefore give
results in ug of C, H, N. These values are then converted to ug/L following the
formulas below.
Blanks are designated on the
analyzer and will be automatically
subtracted from the value of any
pellet entered as a “sample” and not
a blank or K factor. For additional information regarding the analyzer or
procedure contact Chris Crockett
(MBL 508 289 7584,
ccrockett@mbl.edu) or Don
Burnette (MBL 508 289 7764) for CHN
availability and costs.